Date: Wed, 12 Nov 2008 20:05:48 -0800
Reply-To: Ben S <phlogiston420@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ben S <phlogiston420@GMAIL.COM>
Subject: troubleshooting a starting problem
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i started having problems with my '86 westy while driving last
weekend. it was our second good rain of the season here in san
francisco, and after an afternoon of wet driving, i experienced the
following phenomenon: if i let the engine speed get below about 2k rpm
(at load or at idle), the engine would start to run poorly. it
stalled out a couple times while i was idling at stoplights. the
strange thing is that each time the engine started to struggle, the
coolant warning light would come on and flash. then, if i revved up
the engine, it would start running smoothly again and the light would
go out.
when i came back the next (dry sunny) afternoon and tried to start
her, i got very little response--the engine was cranking nice and
strong but hardly even sputtering or missing... just cranking and
cranking. eventually it started and i got home. while i was driving
the power seemed normal (no missing) as long as i kept the engine
above 2k. once i parked i started poking around in the engine.
here's what i found:
the heater in the crankcase breather hose was unplugged. plugging it
back in did not help. the throttle switch was reading open circuit
with the throttle closed. i put a jumper wire in the connector to it
(to simulate a closed switch because i was too lazy to adjust it) and
this did not help either. i tried unplugging the temp II sensor.
this did not help. i verified that the idle air controller was
"vibrating" with the ignition switch on. i checked the resistance of
the air flow sensor and it was in spec. i checked the resistance of
the air temp sensor (same connector) and it was maybe a hundred ohms
over the value given in bently for 68degF (ambient temp was 71deg
according to my dash thermo). primary and secondary dc resistance
were also in spec on the ignition coil.
my engine has 175k on the clock. my ignition wires are the good bosch
ones with oem connectors and have 51k miles on them. spark plugs have
about 15k miles. i changed the cap & rotor when i did the wires.
visual inspection showed visible pitting on the contact surface of the
rotor.
what kind of component failures would cause this kind of issue? when
i've had ignition system problems before (arcing from the wires or
fouled plugs) the problems came on slowly and mainly manifested at
high rpm... this problem appeared drastically and immediately with no
warning. i'm thinking it must be either the hall sensor or 02 sensor.
what's the best way to troubleshoot these without just throwing new
parts at my engine??
Ben.
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